I have seen requests for adding better support for watering restrictions for flex schedules in other threads. It looks like flex and water as needed scheduling will water today if the current moisture level is below the allowed depletion level. This works well if the schedule can run any day. However, in the case of 2 watering days per week (say Monday and Thursday), I think the trigger for watering a zone on Monday would be to water if the zone will be depleted to 'wilt' level by Thursday (the next available watering day on the schedule) if the Monday watering is skipped.
Sounds easy in theory, but you would need to work out whether to rely on predicted weather forecast data to calculate predicted precipitation and evapotranspiration, or merge the weather forecast with historical data. You might want to have a threshold like the weather intelligence feature for including predicted rainfall. Of course, the further out in the future, the less reliable the weather forecast.
Has this approach been considered yet?